People are now being asked to wear face masks when in busy outdoor areas.
Taoiseach Micheál Martin announced the advice as part of the plan to reopen the country during December.
Until now, people have been advised to wear face masks in certain indoor circumstances - with coverings required by law in the likes of shops and public transport.
However, Mr Martin said the advice is now being updated.
Addressing the nation, he said: "In July, we introduced guidance on wearing masks indoors and this has had an incredibly positive impact.
"We are now adding to that guidance. From 1st December, people will be asked to also wear their masks outdoors on busy streets, within crowded indoor workplaces and in places of worship."
Asked during a press briefing about what is meant by a busy street, the Taoiseach said people should use their "common sense".
He said: "I think we know what a busy street is or a crowded street is... Henry Street, Grafton Street, Patrick's Street...
"In the run-up to Christmas, they're going to be busy - and in many ways they'll almost be the equivalent of the shopping mall or shopping centre.
"NPHET were providing this advice as well, and some reputable infectious disease consultants in this country - Luke O'Neill and others - have been campaigning for the wearing of masks for quite some time."
He also confirmed an €80 fine - which applies for people who refuse to wear a mask on public transport or shops - will not apply for people not wearing masks in crowded outdoor areas.